Impact of femtosecond laser-assisted in situ keratomileusis on retinal ganglion cell function.

PURPOSE: To analyse the effect of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) on the electrical response of retinal ganglion cells using pattern electroretinography (pERG). METHODS: This was a longitudinal, prospective, observational pilot study. We included consecutive myopic patients who underwent FS-LASIK to correct up to 6 dioptres of myopia and up to 2 dioptres of astigmatism. Patients with excessive blinking or tearing and those with Snellen uncorrected visual acuity less than 0.9 dec on postop day 1 were excluded. Diopsys NOVA® (Diopsys Inc., NJ) pERG records, using high- and low-contrast patterns, were obtained 16 h and 1 month after FS-LASIK was performed. Magnitude (µV), Magnitude D (µV), Magnitude D/Magnitude ratio and signal-to-noise ratio (dB) were analysed. Wilcoxon test for nonparametric paired data was employed. RESULTS: pERG data from 24 eyes were analysed from 24 patients who underwent FS-LASIK. Mean age was 35.79 ± 9.86 years. Mean preoperative refraction was -2.69 ± 7.6 D (spherical) and -0.38 ± 0.40 D (cylinder). Mean surgical time was 56.88 ± 7.6 s. No statistically significant differences were obtained for any of the studied parameters when comparing 16 h with 1 month after FS-LASIK, with the exception of Magnitude with low contrast, which increased from 1.21 ± 0.2 to 1.39 ± 0.29 µV at 16 h and 1 month postoperatively, respectively (p = 0.03). CONCLUSIONS: FS-LASIK seems to induce a mild and transitory defect in retinal ganglion cell function. Only a mild decrease was detected in the magnitude value for low-contrast stimuli when pERG was performed 16 h postoperatively, and it returned to normal 1 month after surgery.

Corneal Ectasia Induced by Prostaglandin Analogues.

Our purpose is to document the first case of unilateral mild corneal ectasia developed in an apparently nonpredisposed cornea after topical latanoprost treatment, and its regression after treatment withdrawal. We describe a 44-year-old man with visual impairment in his left eye (OS) and a past medical history of myopic refraction and ocular hypertension with latanoprost treatment, the rest of ocular examination was normal. A decrease in visual acuity was observed with a refractive change. Corneal tomography showed features of mild corneal ectasia in his OS. Topical prostaglandin analogue therapy was removed and replaced by other antiglaucoma topical treatment. Corneal tomography returned to normal, an improvement in the quality of vision was observed and refractive astigmatism recovered to baseline values. This case illustrates that topical latanoprost does affect the matrix metalloproteinases balance in corneal extracellular matrix, and subsequently may produce a corneal weakening. Corneal biomechanical features and corneal stiffness do probably recover after topical prostaglandin analogues withdrawal.

Thinner retinal nerve fibre layer in healthy myopic eyes with thinner central corneal thickness.

PURPOSE: Thinner central corneal thickness (CCT) is a risk factor for conversion from ocular hypertension to glaucoma and for disease progression. However, little is known about the relationship between CCT and characteristics of the optic nerve and the retinal nerve fibre layer (RNFL) in non-glaucomatous eyes. Because myopic eyes may pose diagnostic challenges when assessed for glaucoma, characterising the relationship between CCT and RNFL in these eyes is clinically relevant. Our aim was to investigate the relationship between CCT and RNFL thickness in non-glaucomatous eyes with small/moderate myopia. METHODS: This was a single-centre, observational, prospective, assessor-masked study. Consecutive eligible patients (myopia ≤ - 6.0 dioptres, astigmatism ≤ 2.0 dioptres) without other ocular or neurodegenerative diseases were included. Based on their CCT, the participants were allocated to group 1 (CCT > 555 µm) or group 2 (CCT < 555 µm). Peripapillary RNFL measurements were performed by a masked observer using the Spectralis OCT platform. RESULTS: Sixty eyes were included in group 1 and 63 in group 2. The CCT in the two groups was significantly different (584.27 ± 22.8 µm vs 522.23 ± 20.03 µm, p = 0.0001). There were no other significant differences in the groups in terms of age, refraction, or intraocular pressure. The peripapillary RNFL thickness was higher (all p < 0.005) in group 1 at several sectors: superior-temporal, inferior-temporal, inferior-nasal, and average. A significant positive correlation between CCT and average RNFL thickness was found for the whole population (r = 0.31, p = 0.0001). CONCLUSION: Otherwise, healthy myopes with thinner CCT have thinner RNFL compared with participants of similar age and refraction with thicker CCT.

A Critical Overview of the Biological Effects of Mitomycin C Application on the Cornea Following Refractive Surgery.

During the last 2 decades, modifying the shape of the cornea by means of laser photoablation has emerged as a successful and popular treatment option for refractive errors. Corneal surface ablation techniques such as photorefractive keratectomy (PRK) and laser-assisted subepithelial keratomileusis (LASEK) offer good refractive results while having a minimal impact on corneal biomechanical stability. Past limitations of these techniques included the long-term regression of refractive outcome and a vigorous healing response that reduced corneal clarity in some patients (giving rise to what is clinically described as "haze"). Mitomycin C (MMC) was introduced as a healing modulator and applied on the corneal surface after refractive surgery to address these drawbacks. This article critically reviews the available evidence on the biological effects, safety, and clinical benefits of the off-label use of MMC in corneal refractive surgery.

Retinal nerve fiber layer thickness after laser-assisted subepithelial keratomileusis and femtosecond LASIK: a prospective observational cohort study.

PURPOSE: Based on the assumption that high levels of intraocular pressure (IOP) during femtosecond laser-assisted in situ keratomileusis (FS-LASIK) may compromise the retinal nerve fiber layer (RNFL), newer femtosecond platforms that operate without causing significant IOP elevation have been developed in recent years. However, this assumption has not been adequately tested. The aim of the current study was to evaluate possible changes in RFNL thickness in nonglaucomatous myopic patients undergoing FS-LASIK using the 60 KHz IntraLase® device that significantly elevates the IOP for an appreciable period of time vs an advanced surface ablation technique (laser-assisted subepithelial keratomileusis, LASEK) that does not induce any IOP elevation. METHODS: This was a prospective, observational, controlled cohort study. One randomly selected eye of 114 consecutive eligible patients was analyzed. Inclusion criteria were myopia up to -6.00 diopters and astigmatism up to -2.00 diopters. As clinically indicated, 50 patients underwent LASEK and 64 underwent FS-LASIK. The RNFL thickness was determined with a spectral-domain optical coherence tomography device preoperatively and 3 months postoperatively by the same masked observer. RESULTS: There was no significant difference in preoperative refractive error, age, or sex between the groups. Preoperatively, central corneal thickness was significantly lower in the LASEK group (529.1±36.1 vs 562.4±31.6 µm, P=0.001). For the LASEK group, there was no significant difference between preoperative and postoperative RNFL thickness in the studied sectors (superior-temporal, temporal, inferior-temporal, average). For the FS-LASIK group, compared to preoperative RNFL measures, statistically significant thicker postoperative values were found for the average RNFL (mean difference: 0.67 µm, 0.7% increase, P=0.008) and the inferior-temporal sector (mean difference: 0.92 µm, 0.6% increase, P=0.02). CONCLUSION: LASIK with a femtosecond platform that induces high intraoperative IOP did not cause RNFL thinning. The observed differences between preoperative and postoperative values are below the axial resolution limit of optical coherence tomography devices.

Assessing the role of ranibizumab in improving the outcome of glaucoma filtering surgery and neovascular glaucoma.

INTRODUCTION: Ranibizumab was the first anti-vascular endothelial growth factor (VEGF) agent approved for the treatment of neovascular age-related macular degeneration. The use of ranibizumab and other anti-VEGF medications in recent years has revolutionized the treatment of several sight-threatening retinal disorders. Emerging evidence has demonstrated that anti-VEGF treatment can offer advantages in the management of other ocular conditions where VEGFs play a key role: ocular scarring following glaucoma filtering surgery and neovascular glaucoma (NVG). Areas covered: We critically review available evidence on the use of ranibizumab as a wound healing modulator in glaucoma filtering surgery and as an adjunct in the management of NVG. Expert opinion: Based on the available evidence and the authors' clinical experience, ranibizumab is a valuable adjunct in the management of NVG. In glaucoma filtering surgery, however, the role of ranibizumab is less clear and does not provide a significant advantage over mitomycin C. Drawbacks for its use in glaucoma include cost, its off-label use, uncertainty and limited evidence on the various routes of administration, the optimal dosing schemes and its toxicity profile. Future advances in ranibizumab delivery systems allowing less frequent dosing may change this treatment paradigm.

Influence of LASEK on Schiøtz, Goldmann and dynamic contour Tonometry.

PURPOSE: Our purpose was to assess the effect of LASEK surgery on ocular rigidity and to compare its effect on intraocular pressure (IOP) readings with Goldmann applanation tonometry (GAT), Schiøtz indentation tonometry (ST) and dynamic contour tonometry (DCT). METHODS: Prospective, observational, single-masked cohort study. One eye per patient from 31 consecutive subjects who underwent LASEK refractive surgery to correct myopia, as well as from 108 non-operated myopic patients, were included. IOP was measured using GAT, DCT, and ST. The coefficient of ocular rigidity (Ko) was obtained from the regression line of the three readings obtained with each weight of the ST. Linear multiple regression analysis was performed with dummy variables to assess the effect of age, central corneal thickness (CCT), and previous refractive surgery on IOP values. RESULTS: Age, CCT, and LASEK surgery explained 23% of the IOP readings with GAT, 11% with DCT, and had no significant influence on ST readings. The IOP readings obtained with GAT and DCT, but not with ST, were significantly different between LASEK and control groups. Significant differences in Ko were observed between LASEK (0.014 mmHg/µL ±0.007) and control groups (0.021 mmHg/µL ±0.013) (P = 0.001). Ko values were not related with age or CCT, in either LASEK or control groups. CONCLUSIONS: ST readings seems to be less affected by LASEK surgery than the other tonometers evaluated. There is a difference in the ocular rigidity between the control and the LASEK eyes that it is not correlated with CCT, so it seems that ST can detect changes in the biomechanical behavior of the LASEK operated corneas.

Effect of Laser in Situ Keratomileusis on Schiøtz, Goldmann, and Dynamic Contour Tonometric Measurements.

PURPOSE: To assess the effect of laser in situ keratomileusis (LASIK) on ocular rigidity and compare its effect on intraocular pressure (IOP) readings with Goldmann applanation tonometry (GAT), Schiøtz indentation tonometry (ST), and dynamic contour tonometry (DCT). PATIENTS AND METHODS: Prospective, observational, single-masked study. Eighty-one patients who underwent myopic LASIK and 108 unoperated myopic control patients were included in the study. The IOP was measured using GAT, DCT, and ST. The coefficient of ocular rigidity (Ko) was obtained from the regression analysis of the 3 readings obtained with each weight of the ST. Linear multiple regression analysis was performed with dummy variables to assess the effects of age, central corneal thickness (CCT), and refractive surgery on measured IOP values. RESULTS: Age, CCT, and previous LASIK explained 39.41% of the IOP readings with GAT, 25.31% with DCT, and 3.28% with ST. LASIK caused a mean decrease of -2.51 mm Hg in IOP readings (P=0.000) with GAT, -1.29 mm Hg (P=0.036) with DCT, and no significant change in IOP readings with ST (P=0.299). Significant differences in the Ko were observed between the LASIK and control groups. The Ko values were unrelated to age and CCT in the LASIK and control groups. CONCLUSIONS: ST seems to be less affected by previous LASIK procedures. There is a difference in the ocular rigidity between the unoperated and LASIK eyes that is not correlated with the CCT. Therefore, ST seems to measure changes in the biomechanical behavior of corneas that underwent LASIK surgery.

Eficacia en la prevención de la regresión posterior a la cirugía LASIK para hipermetropía / Efficacy of long-term topical steroid treatment to prevent regression after hyperopic LASIK

Evaluar la eficacia del tratamiento corticoideo tópico prolongado en pacientes operados con LASIK hipermetrópico. Material y métodos: Se realizó un estudio prospectivo, de observación y enmascarado. Los pacientes candidatos a cirugía LASIK para la corrección de baja y moderada hipermetropía fueron asignados aleatoriamente a recibir tratamiento tópico corticoideo (dexametasona) durante una semana (grupo control) o un mes (dexametasona, la primera semana, y fluorometalona, las tres siguientes),en el grupo de estudio. Se comparó la refracción final manifiesta en ambos grupos. Resultados:Analizamos 105 ojos en cada grupo (estudio y control). El equivalente esférico medio preoperatorioera 3.17 desviación estándar (DE) ± 2.82 DE y 3.39 DE ± 2.65 DE en los grupos de estudio y control, respectivamente (p = 0.6). La refracción final manifiesta a los tres meses fue 0.62 DE ± 0.68 DE y 0.6 DE± 0.3 DE en el grupo de estudio y control, respectivamente (p = 0.6). Conclusión: La regresión refractivatras el LASIK hipermetrópico no parece poder modularse por el mayor o menor tratamiento corticoideotópico...

Orbscan topography in primary open-angle glaucoma.

PURPOSE: To compare anterior and posterior corneal curvatures between eyes with primary open-angle glaucoma (POAG) and healthy eyes. METHODS: This is a prospective, cross-sectional, observer-masked study. A total of 138 white subjects (one eye per patient) were consecutively recruited; 69 eyes had POAG (study group), and the other 69 comprised a group of healthy control eyes matched for age and central corneal pachymetry with the study ones. Exclusion criteria included any corneal or ocular inflammatory disease, previous ocular surgery, or treatment with carbonic anhydrase inhibitors. The same masked observer performed Goldmann applanation tonometry, ultrasound pachymetry, and Orbscan II topography in all cases. Central corneal thickness, intraocular pressure, and anterior and posterior topographic elevation maps were analyzed and compared between both groups. RESULTS: Patients with POAG had greater forward shifting of the posterior corneal surface than that in healthy control eyes (p < 0.01). Significant differences in anterior corneal elevation between controls and POAG eyes were also found (p < 0.01). CONCLUSIONS: Primary open-angle glaucoma eyes have a higher elevation of the posterior corneal surface than that in central corneal thickness-matched nonglaucomatous eyes.

Asymmetric dimethyloarginin (ADMA) concentration in the aqueous humor of patients with exfoliation syndrome or exfoliative glaucoma.

BACKGROUND: Asymmetric dimethyloarginin or dimethylarginin (ADMA) is a marker and maker of oxidative stress. It is elevated in several pathological conditions, such as hyperhomocysteinemia and endothelial dysfunction, which have also been reported in patients with exfoliation syndrome (XFS), or exfoliative glaucoma (XFG). We evaluated ADMA levels in the aqueous humor of XFS and XFG patients. METHODS: This study included 48 aqueous samples; 16 from cataract patients with XFS, 16 from cataract patients with XFG and 16 from age-matched cataract control patients. ADMA levels were determined employing a commercial ELISA kit. RESULTS: ADMA concentration was significantly greater in XFG patients (0.398 ± 0.026 µM) compared to either XFS (0.168 ± 0.028 µM; p < 0.0001) or normal cataract controls (0.245 ± 0.025 µM; p = 0.0002). In contrast, no significant difference was detected for ADMA levels in the aqueous of XFS patients as compared to normal controls (p = 0.0477). CONCLUSIONS: Aqueous humor ADMA concentration is significantly elevated in XFG patients supporting the view that oxidative stress plays a key role in XFG pathobiology. The lower level of this marker in XFS suggests that the development of XFG is a prerequisite for ADMA elevation.

Effect of acute increases of intraocular pressure on corneal pachymetry in eyes treated with travoprost: an animal study.

PURPOSE: To evaluate "in vivo" the effect of topical travoprost on the central corneal thickness (CCT) of rabbit eyes, and the changes in the CCT after acute increases of intraocular pressure (IOP) in these eyes. MATERIALS AND METHODS: This is an interventional, prospective, case-control, masked study. Topical travoprost was applied once daily for one month to the right eye of six New Zealand male rabbits, the left eye of each animal served as control. The baseline CCT and IOP were measured under general anesthesia. After the IOP was stabilized at 15 and 30 mmHg, as registered by direct cannulation of the anterior chamber, CCT measurements were measured again at both pressure levels. RESULTS: The baseline CCT was thicker in eyes previously treated with travoprost (study group) than in control eyes (p < 0.01). The CCT decreased in both groups when IOP was raised to 15 and 30 mmHg, and there were no statistically significant difference in absolute CCT values between study and control eyes at any of the IOP levels (p = 0.5). However, the amount of CCT decrease from baseline values was greater in eyes previously treated with travoprost (study group) than in control ones, at both 15 and 30 mmHg IOP levels (p = 0.01 and 0.02, respectively). CONCLUSIONS: Rabbit corneas treated with topical travoprost show a different strain response to acute increases in IOP than control eyes.

Prostanoids for the management of glaucoma.

BACKGROUND: Prostanoids are the newest pharmacologic group of ocular hypotensive drugs for clinical management of glaucoma. The group includes four chemical compounds structurally derived from naturally-occurring prostaglandin (PG) F(2). Prostanoids have been divided into PG analogues (unoprostone, latanoprost and travoprost) and prostamides (bimatoprost) because of differences in molecular structures. The drugs share a novel mechanism of action that produces a potent ocular hypotensive effect and a novel local adverse effect of increased iridial pigmentation. OBJECTIVE: To summarise the pharmacologic and clinical data regarding the effectiveness and safety of prostanoids in clinical glaucoma management. METHODS: The review was supported by a literature search of peer-reviewed publications, based on medical information available in databases such as PubMed. RESULTS/CONCLUSION: The prostanoids began a treatment revolution not only because of their novel mechanism of action but also as a result of a new local side effect.

Phakic refractive lens (Medennium) for correction of +4.00 to +6.00 diopters: 1-year follow-up.

PURPOSE: To study the efficacy and safety of phakic refractive lens (PRL) implantation to correct high hyperopia. METHODS: Inclusion criteria for this prospective, observer-masked, interventional study were spherical equivalent > or =+4.00 diopters (D) of cycloplegic hyperopia, best spectacle-corrected visual acuity (BSCVA) > or =0.5, anterior chamber depth > or =3 mm, and mesopic pupil size < or =6 mm. Lenses were implanted in all cases under regional anesthesia using forceps. RESULTS: Sixteen eyes of nine patients were included in the study. Mean preoperative spherical equivalent refraction was +5.65+/-1.41 D (range: +3.25 to +5.75 D). Mean 1-year postoperative spherical equivalent refraction was +0.07+/-0.43 D (range: -0.50 to 0.75 D). Fifteen (93.75%) eyes were within +/-0.50 D of emmetropia, and 16 (100%) eyes were within +/-1.00 D of emmetropia. Safety and efficacy indexes were 0.9 and 0.8, respectively. Eight (50%) eyes needed LASIK to correct residual astigmatism. Five (31.25%) eyes lost one line of BSCVA; no eye lost two or more lines of BSCVA. The BSCVA did not increase in any eye. No significant intraocular complications developed. CONCLUSIONS: Phakic refractive lens implantation to correct high hyperopia seems to be a safe and accurate procedure. A mild but significant loss in BSCVA can be anticipated.

Comparison of silicone and non-silicone hydrogel soft contact lenses used as a bandage after LASEK.

PURPOSE: To evaluate two different soft contact lens materials for continuous-wear bandage contact lenses after laser epithelial keratomileusis (LASEK). METHODS: A prospective, observer-masked study was conducted of 32 eyes of 16 consecutive patients. Inclusion criteria were candidates for bilateral LASEK, myopia of < or = -6.00 diopters (D), astigmatism < -1.50 D, and bilateral best spectacle-corrected visual acuity of 20/20 or better. Patients were randomly selected for a balafilcon A (PureVision; Bausch & Lomb) bandage contact lens in one eye and a poly-2-hydroxyethylmethacrylate-co-methacrylate glycerol (EquiS 60; mark'ennovy) in the fellow eye. Corneal epithelial status, conjunctival and limbal hyperemia, lens movement, contact lens debris, and the responses to a subjective comfort questionnaire were assessed postoperatively. The parameters were evaluated preoperatively and 1 and 5 days postoperatively. Paired Student t test and chi-square tests were used when appropriate. RESULTS: Thirty-two eyes of 16 consecutive patients who underwent LASEK to correct low to moderate myopia were analyzed. The mean spherical equivalent refraction was -3.25 D. There was no difference in conjunctival or limbal hyperemia, contact lens debris, or subjective comfort between lenses at any postoperative visit. In contrast, the corneal epithelial status was statistically better in the eyes with a silicone bandage contact lens 5 days after LASEK (P = .01). CONCLUSIONS: The results suggest that the bandage contact lens material used after LASEK affects the corneal epithelial healing process.